1. Field of the Invention
This invention relates to the field of information display systems wherein remote terminals present information originally entered at a central processor, and in particular to such systems having coin operated remote terminals.
2. Description of the Prior Art
Data access systems having a plurality of remote terminals in communication with a central processor are well known in the art. These systems are commonly termed "time share systems". In common embodiment, the remote terminal is equipped with a full keyboard and CRT (cathode ray tube) display. In such systems, the remote terminal is programmed for input and output to the central processor, and is nearly equivalent in capability to the operator's monitor terminal at the central processor. In any event, upon operation of the keyboard the user is able to access data in the central processor's memory.
Of course, the capabilities of remote terminals may be limited by programming. Certain commands which may endanger the operation of the system, or possibly allow a breach of security, can be made unacceptable at the remote terminal by appropriate programming of the central processor controlling the remote. Therefore, it is not remarkable that a remote terminal be limited to simple commands which might call up a display of data.
In prior art systems, even limited function remote terminals must communicate with the central processor in order to call up a display of data. This attribute of prior art systems has a number of implications which bear on the reliability and expense of data display systems. Inasmuch as remote terminals must be equipped with sufficient switches to allow the user to select and initiate a data transmission, the remote terminals must be sophisticated in both hardware and software. If phone lines are used for the transmissions to and from the central processor, each remote must be equipped with a modulater/demodulater (modem) to convert digital data signals into tones necessary for phone transmission. If the remote unit is usable for some reason to contact the central processor, no information can be displayed.
At the other side of the system, the central processor must also be sophisticated enough to receive queries from remote units, process the information and transmit a response. In the normal time share system, several transmissions will be required before data can be requested and transmitted to the remote. It is therefore necessary that both the central processor and remote terminal be sophisticated enough to conduct a number of receptions and transmissions in order to service an information request from any single remote. Should the central processor be down, the entire system will be down, and no information will be displayed.
In an information display system where certain parameters are repeatedly displayed, yet the values of such parameters are apt to change over time, prior art systems would require that the central processor service each data query, whether or not the value of the requested parameter has changed during the interval since the last query. In such systems, the central processor becomes a bottleneck. Any problems in the central processor, data transmission network, etc. preclude the possibility of information display.
The present invention contemplates a continuously-available information store at the remote readouts. There is no need for the remote terminal to ever transmit to the central processor unit. Rather, the central processor is adapted to update the remote information store only when necessary due to a change in data value. Accordingly, information is always available at the remote for display. Alternatively, periodic transmissions may be programmed, whereby information is regularly updated without regard to the occurrence or non-occurrence of information queries at the remotes.
In an embodiment adapted for transmission of information periodically, as opposed to transmission upon a change in a data value, the full costs of operation are known from the outset, without reference to the number of data queries at the remotes, or to the rate of change of data values. The system builder can calculate expenses including an unchanging amount of central processor time and an unchanging number of phone calls, and can more readily plan the system. If desired, different terminals can be updated at different frequencies. For example, terminals adapted to display information updated hourly might charge a first price, while terminals updated at five (5) minute intervals or upon every change of data value might charge a significantly higher price then the first. Terminals designed to display stock prices updated frequently would charge more than less-frequently updated weather terminals.
A coin operated time share terminal system is disclosed in U.S. Pat. No. 3,938,093-Riess. Examination of the system disclosed by Riess will indicate that there are substantial savings in system complexity and reliability to be realized from the system of the present invention. Like the present invention, the Riess system is adapted to operate upon receipt of a coin. Unlike the present system, the Riess system conducts two way communication with the central processor, and has only such remote storage capacity as necessary to conduct such two way communications. Both the remote unit and the central processor must be equipped with complete modems, the remote terminal requires a full keyboard, and since the display requests may be unsuccessful, a controller adapted to return coins is required.
The present system requires no keyboard or switches of any kind in its simplest embodiment. Should the system be configured for display of a selection of possible displays, then only a simple switch network will be required, much less than a full keyboard. The central processor need not be accessed at all for a data query. Rather, the information stored in the remote memory is displayed upon query. The control processor, which only transmits the data, is not concerned with individual queries and thus saves time. No data communication reliability problems are encountered during an information query, and therefore information is always available. A coin need never be returned, and a user need never be frustrated.